The present invention relates to an optical apparatus having a driving source for driving a lens in an optical axis direction, and particularly, to an optical apparatus which includes a vibration type linear actuator for use as a driving source.
Some optical apparatuses include a vibration type linear actuator for use as a driving source for driving a lens (for example, see Japanese Patent Laid-Open No. 10(1998)-90584).
In the optical apparatuses proposed in Japanese Patent Laid-Open No. 10(1998)-90584 having the vibration type linear actuator, the vibration type linear actuator is formed of a vibrator which produces vibration through an electromechanical energy conversion action and a contact member which is in press contact with the vibrator. The vibrator is fixed to a lens holding member, the contact member is fixed to a stationary member of a lens barrel, and the vibrator is caused to produce driving vibration, thereby moving the lens holding member together with the vibrator, or the contact member is fixed to the lens holding member, the vibrator is fixed to the stationary member of the lens barrel, and the vibrator is caused to produce driving vibration, thereby moving the lens holding member together with the contact member.
The description will be made of the lens barrel proposed in Japanese Patent Laid-Open No. 10(1998)-90584 using FIGS. 21 and 22.
In FIGS. 21A to 21D, reference numeral 901 denotes a lens holding frame, 902 denotes a guide bar which guides the lens holding frame 901 in the optical axis direction. Reference numeral 904 denotes a vibrator, 905 a supporting portion which supports the vibrator 904, 906 a contact member which is in press contact with the vibrator 904, and 907 a biasing member which produces the press contact force acting between the vibrator 904 and the contact member 906.
In FIG. 22, reference numeral 911 a denotes a lens holding frame, and 913 a guide bush which is attached to the lens holding frame 911 and engages with a guide bar 930 in a movable condition in the optical axis direction. Reference numeral 920 denotes a vibrator holding frame which is provided on the guide bush 913, and 925a and 925b supporting portions which support a vibrator 923. Reference numeral 922 denotes a contact member which is fixed to a lens barrel main body, and 926 a spring which produces the press contact force acting between the vibrator 923 and the contact member 922.
As shown in FIGS. 21C and 21D, in a case where the vibrator 904 or the contact member 906 is supported only by the biasing member 907, though the press contact between the vibrator 904 and the contact member 906 is ensured, there is no structure that supports the vibrator 904 or the contact member 906 in the optical axis direction. This causes a deformation of the biasing member 907 in the lens driving direction, thereby deteriorating the accuracy of the driving position of the lens holding frame 901.
On the other hand, as shown in FIGS. 21A, 21B, and 22, in a case where the vibrator 904 or 923 is supported by the supporting member 905 or 925a, 925b in a movable condition only in a direction perpendicular to the press contact surface, a so-called point contact state or line contact state is generated between the vibrator and the contact member by relative inclinations of the guide bar 902 or 930, the supporting portion 905 or 925a, 925b, and the contact member 906 or 922. This reduces the driving force in comparison with the driving force generated by the surface contact of the vibrator and the contact member.
Further, the biasing force (or spring force) generated by the biasing member which brings the vibrator and the contact member into press contact with each other is extremely large, so that the reaction force of the press contact force acting on the engagement part of the lens holding member and the guide bar increases the friction force (or driving load) generated in the engagement part in the driving direction. This causes problems that an increase of the size and output power of the vibration type linear actuator is required, a fine lens drive cannot be performed, and the engagement part is worn.